1) Field of the Invention
The present invention relates to energization of a motor, and more specifically, to a motor driving apparatus that controls a power source of a lens barrel motor of a digital camera, a digital camera, and a motor controlling method.
2) Description of the Related Art
Conventionally, a lens barrel in cameras, such as a digital camera, is collapsibly mounted on the cameras to put emphasis on portability. Furthermore, there is a method for high-speed activation. In the method, a high voltage is applied at a time of activation of a motor. Generally, by changing voltage of a series regulator connected to a power source, supply voltage is directly used when a motor is driven at a high speed, and the voltage is lowered during the motor is driven at an ordinary speed to reduce an electric current for the motor.
As a conventional technology, there is a “motor driving apparatus” that prevents severe shock and pulling-out of synchronism, and uncomfortable vibration noise that occur during acceleration control used when the motor is to be started. Such a technology is disclosed in, for example, Japanese Patent Application Laid-Open Application No. 2002-78385. Moreover, there is a “motor drive controller” that converges vibration control after a motor startup within a short time, and performs phase control and vibration control more accurately after the convergence. Such a technology is disclosed in, for example, Japanese Patent Application Laid-Open Application No. 2003-189692.
However, in the conventional technology, power cannot sufficiently be reduced because the supply voltage is partially consumed by a series regulator.
In the technology disclosed in Japanese Patent Application Laid-Open Application No. 2002-78385, as to a method in which the action of the power source itself is changed at a time of activation, although an input filter circuit is changeable, change in voltage due to change of feedback resistance is not taken into consideration. In addition, a method in which vibration is suppressed by control with sine waves is proposed in the technology disclosed in Japanese Patent Application Laid-Open Application No. 2003-189692, however, change in voltage due to change of feedback resistance is not taken into consideration.